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Rearrange storage of data in xl_running_xacts.

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Previously we stored all xids mixed together.
Now we store top-level xids first, followed
by all subxids. Also skip logging any subxids
if the snapshot is suboverflowed, since there
are potentially large numbers of them and they
are not useful in that case anyway. Has value
in the envisaged design for decoding of WAL.
No planned effect on Hot Standby.

Andres Freund, reviewed by me
This commit is contained in:
Simon Riggs
2012-12-02 19:39:37 +00:00
parent c11130690d
commit 5c11725867
4 changed files with 52 additions and 25 deletions
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8
src/backend/storage/ipc/standby.c
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@@ -778,6 +778,7 @@ standby_redo(XLogRecPtr lsn, XLogRecord *record)
RunningTransactionsData running;
running.xcnt = xlrec->xcnt;
running.subxcnt = xlrec->subxcnt;
running.subxid_overflow = xlrec->subxid_overflow;
running.nextXid = xlrec->nextXid;
running.latestCompletedXid = xlrec->latestCompletedXid;
@@ -897,6 +898,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
XLogRecPtr recptr;
xlrec.xcnt = CurrRunningXacts->xcnt;
xlrec.subxcnt = CurrRunningXacts->subxcnt;
xlrec.subxid_overflow = CurrRunningXacts->subxid_overflow;
xlrec.nextXid = CurrRunningXacts->nextXid;
xlrec.oldestRunningXid = CurrRunningXacts->oldestRunningXid;
@@ -912,7 +914,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
{
rdata[0].next = &(rdata[1]);
rdata[1].data = (char *) CurrRunningXacts->xids;
rdata[1].len = xlrec.xcnt * sizeof(TransactionId);
rdata[1].len = (xlrec.xcnt + xlrec.subxcnt) * sizeof(TransactionId);
rdata[1].buffer = InvalidBuffer;
lastrdata = 1;
}
@@ -931,8 +933,8 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts)
CurrRunningXacts->nextXid);
else
elog(trace_recovery(DEBUG2),
"snapshot of %u running transaction ids (lsn %X/%X oldest xid %u latest complete %u next xid %u)",
CurrRunningXacts->xcnt,
"snapshot of %u+%u running transaction ids (lsn %X/%X oldest xid %u latest complete %u next xid %u)",
CurrRunningXacts->xcnt, CurrRunningXacts->subxcnt,
(uint32) (recptr >> 32), (uint32) recptr,
CurrRunningXacts->oldestRunningXid,
CurrRunningXacts->latestCompletedXid,